Display, article with display, and method of observing display

ABSTRACT

A display that exhibits improved anti-counterfeiting effects. The display includes an uneven-structure-forming layer having an uneven structure on one surface and a reflecting layer that covers at least part of an unevenly structured surface. In the display, the uneven-structure-forming layer includes a first region group including a plurality of first regions, each first region including a flat part and a plurality of convexities or a plurality of concavities, the top surface of each of the convexities or the bottom surface of each of the concavities is substantially parallel to a surface of the flat part; distances between the centers of adjacent convexities or concavities are not equal; the convexities have a uniform height, or the concavities have a uniform depth; the first region group is formed, with the first regions arrayed inside at a regular pitch.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation application filed under 35 U.S.C. §111(a) claiming the benefit under 35 U.S.C. §§ 120 and 365(c) ofInternational Application No. PCT/JP2016/004591, filed on Oct. 14, 2016,which is based upon and claims the benefit of priority to Japan PriorityApplication No. 2015-205770, filed on Oct. 19, 2015, the disclosures ofwhich are all hereby incorporated herein by reference in theirentireties.

TECHNICAL FIELD

The present invention relates to a display that providesanti-counterfeiting, decorative, and/or aesthetic effects. Moreparticularly, the present invention relates to a display that providesanti-counterfeiting effects applicable to security devices for papercurrencies, identifications (IDs), and brand protection (BP).

BACKGROUND OF THE INVENTION

Valuable stock certificates, such as gift tickets or checks, cards, suchas credit cards, cash cards, or ID cards, and certificates, such aspassports or driver's licenses, are each typically adhered with adisplay having visual effects different from those of a normal printedobject to prevent counterfeiting of these articles. Circulation ofcounterfeit articles besides certificates is also becoming a socialproblem in recent years. Therefore, there are increasing opportunitiesof applying similar anti-counterfeiting technique to such articles aswell.

Known displays having visual effects different from those of normalprinted objects include, for example, a display provided with adiffraction grating (PTL 1). Depending on the observation angle, thewavelength of diffracted light reaching the observer's eyes varies. Withthis variation, the observer recognizes iridescent change in a displaycolor.

Also known is a display that scatters illumination light and displays acolor with high chroma by virtue of a fine uneven structure (PTLs 2 to5). This display is characterized in that a color change is preventedfrom being displayed which is observed in a display having a diffractiongrating.

CITATION LIST

Patent Literature [PTL 1] JPAH04-136810; [PTL 2] JP4983899; [PTL 3]JP4983948; [PTL 4] JP5143855; [PTL 5] JP5570210

SUMMARY OF THE INVENTION Technical Problem

However, under circumstances that every article needing measures forpreventing counterfeiting uses the above technique, this technique hascome to be widely known. Therefore, a display with improvedanti-counterfeiting effects is still sought.

The present invention aims to provide a display that exhibits improvedanti-counterfeiting effects and an article with the display.

Solution to Problem

The present invention relates to a display including anuneven-structure-forming layer having an uneven structure on one surfacethereof and a reflecting layer that covers at least part of an unevenlystructured surface of the uneven-structure-forming layer. In thedisplay, the uneven-structure-forming layer includes a first regiongroup including a plurality of first regions, each first regionincluding a flat part and a plurality of convexities or a plurality ofconcavities, the top surface of the convexities or the bottom surface ofthe concavities is substantially parallel to a surface of the flat part;distances between the centers of adjacent convexities or concavities arenot equal, the convexities have a uniform height, or the concavitieshave a uniform depth; and the first region group is formed, with thefirst regions arrayed inside at a regular pitch.

The present invention encompasses an article with a display, the articlebeing provided with the display described above and an article thatcarries the display.

The present invention further relates to an observing method of adisplay using a point light source to observe a display including anuneven-structure-forming layer having an uneven structure on one surfaceand a reflecting layer that covers at least part of an unevenlystructured surface of the uneven-structure-forming layer, In thedisplay, the uneven-structure-forming layer includes a first regiongroup including a plurality of first regions, each first regionincluding a flat part and a plurality of convexities or a plurality ofconcavities, the top surface of the convexities or the bottom surface ofthe concavities is substantially parallel to the surface of the flatpart; distances between the centers of adjacent convexities orconcavities are not equal; the convexities have a uniform height, or theconcavities have a uniform depth; and the first region group is formed,with the first regions arrayed inside at a pitch of 1 μm-100 μm.

The present invention further relates to an observation method using alaser light to observe a display including an uneven-structure-forminglayer having an uneven structure on one surface and a reflecting layerthat covers at least part of an unevenly structured surface of theuneven-structure-forming layer. In the display, theuneven-structure-forming layer includes a first region group including aplurality of first regions, each first region including a flat part anda plurality of convexities or a plurality of concavities, the topsurface of the convexities or the bottom surface of the concavities issubstantially parallel to the surface of the flat part; distancesbetween the centers of adjacent convexities or concavities are notequal; the convexities have a uniform height, or the concavities have auniform depth; and the first region group is formed, with the firstregions arrayed inside at a pitch of 1 μm-300 μm.

Advantageous Effects of the Invention

The display and the article with the display of the present inventionproduces a color change due to a periodic structure according to thechange of an observation angle (hereinafter also referred to as“iridescent change due to a periodic structure”), and displays a colorwith high chroma by virtue of the scattered light (hereinafter alsoreferred to as “structural color by virtue of the scattered light” or“structural color”). The display and the article thereby exhibitimproved anti-counterfeiting effects than conventional ones.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic plan view illustrating an example of a displayaccording to the present invention.

FIG. 1B is an enlarged view of a part circled by the dash-dot line shownin FIG. 1A.

FIG. 1C is a cross-sectional view taken along the line IC-IC shown inFIG. 1B.

FIG. 2 is a schematic diagram illustrating an example of an unevenstructure of a first region of an uneven-structure-forming layer.

FIG. 3 is a schematic diagram illustrating another example of an unevenstructure of a first region of an uneven-structure-forming layer.

FIG. 4 is a schematic diagram illustrating another example of an unevenstructure of a first region of an uneven-structure-forming layer.

FIG. 5 is a schematic diagram illustrating another example of an unevenstructure of a first region of an uneven-structure-forming layer.

FIG. 6 is a schematic diagram illustrating another example of an unevenstructure of a first region of an uneven-structure-forming layer.

FIG. 7 is a schematic diagram illustrating another example of an unevenstructure of a first region of an uneven-structure-forming layer.

FIG. 8 is a schematic diagram illustrating an example of an unevenstructure of a first region group.

FIG. 9 is a schematic diagram illustrating another example of an unevenstructure of a first region group.

FIG. 10 is a schematic diagram illustrating another example of an unevenstructure of a first region group.

FIG. 11 is a schematic diagram illustrating another example of an unevenstructure of a first region group.

FIG. 12 is a schematic diagram illustrating another example of an unevenstructure of a first region group.

FIG. 13 is a schematic diagram illustrating an example of an unevenstructure of an aspect in which mutually different first region groupsare combined.

FIG. 14 is a schematic diagram illustrating another example of an unevenstructure of an aspect in which mutually different first region groupsare combined.

FIG. 15 is a schematic diagram illustrating another example of an unevenstructure of a first region group.

FIG. 16 is a schematic diagram illustrating how a diffraction gratingemits primary diffracted light.

FIG. 17 is a schematic diagram illustrating how an uneven structure of afirst region of an uneven-structure-forming layer emits scattered light.

FIG. 18 is a schematic diagram illustrating how illumination light whichis incident on an uneven structure provided at a first region and isreflected on a flat part and on the bottom surface of a concavity.

FIG. 19 is a schematic plan view illustrating an example of an articlewith a display of the present invention.

DESCRIPTION OF THE REPRESENTATIVE EMBODIMENTS

The embodiments of the present invention will be described in detail. Inthe following description, reference will be made to the drawings asappropriate, but embodiments illustrated in the drawings are examples ofthe present invention. It will be understood that the embodimentsdiscussed below are intended to be representative of the presentinvention. The present invention is not limited to these aspects. Notethat identical reference signs are given to components that exhibit anidentical or similar function, thereby omitting repetitive descriptionon occasions. Also note that a scale ratio in each drawing isexaggerated for convenience of description and may possibly differ froman actual ratio. Further, in the present specification, a “-” sign meansthat a lower limit value and an upper limit value before and after thesign are inclusive.

<Display>

The display according to the present invention includes anuneven-structure-forming layer having an uneven structure on one surfacethereof and a reflecting layer that covers at least part of an unevenlystructured surface of the uneven-structure-forming layer. Theuneven-structure-forming layer has a first region group constituted by aplurality of first regions and has a specific uneven structure in thefirst region. The first regions are regularly arranged at a regularpitch.

FIG. 1A is a plan view schematically illustrating an example of adisplay according to the present invention. FIG. 1B is an enlarged viewof a part circled by the dash-dot line shown in FIG. 1A. FIG. 2B is across-sectional view taken along the line IC-IC shown in FIG. 1B. InFIGS. 1A to 1C, the X direction and the Y direction are parallel to adisplay surface, while being perpendicular to each other. Further, the Zdirection is perpendicular to the X and Y directions.

The display according to the present invention includes anuneven-structure-forming layer having an uneven structure on one surfacethereof and a reflecting layer that covers at least part of an unevenlystructured surface of the uneven-structure-forming layer. The display inthe example shown in FIG. 1C includes a substrate 2, anuneven-structure-forming layer 4, which has a concavity structure on asurface opposite to the substrate 2, and a reflecting layer 6, whichcovers the concavity surface of the uneven-structure-forming layer 4. Inthis example, a substrate 2 side serves as a front side (observer side),and a reflecting layer 6 side serves as a rear side. In the presentinvention, the uneven-structure-forming layer 4 may be provided with aconvexity structure (convexities) in place of the concavity structure(concavities). Whether to form (concavities) or convexities depends onthe surface where the uneven structure is formed. Forming recesses onthe surface produces a concavity structure (concavities), whileproviding projections on the surface produces a convexity structure(convexities). Components of a display 10 will be described below.

(Substrate 2)

A substrate 2 has light transmission properties. The substrate 2 istypically transparent and, in particular, colorless and transparent.Examples of the material that can be used as the substrate 2 include arelatively highly heat-resistant resin such as polyethyleneterephthalate (PET) and polycarbonate (PC).

The substrate 2 may be a film or sheet that can be used alone. Thesubstrate 2 serves as a base of the uneven-structure-forming layer 4while protecting the uneven-structure-forming layer 4. The substrate 2can be omitted.

(Uneven-Structure-Forming Layer 4)

The uneven-structure-forming layer 4 is permeable to light. Theuneven-structure-forming layer 4 is typically transparent and, inparticular, colorless and transparent.

The uneven-structure-forming layer 4 has a first region group Gconstituted by a plurality of first regions R1 and has an unevenstructure in each first region R1. The uneven structure includes a flatpart and a plurality of convexities or a plurality of concavities. Inthe example shown in FIG. 1C, a flat part 4 b is provided so as to fillthe space between each of the plurality of concavities 4 a. The firstregion group G may have a flat region F as in the example shown in FIG.11.

The uneven-structure-forming layer 4 may have a second region R2, whichhas a structure different from that of uneven structure in the firstregion R1. The structure of the second region R2 is not particularlylimited as long as it is different from the uneven structure in thefirst region R1. Examples of the structure of the second region R2include a diffraction grating, a scattering structure, a light-absorbentmoth eye structure, a structure in which a light-absorbent moth-eyestructure and a light diffraction structure are combined, or a flatstructure. When a diffraction grating is provided in the second regionR2, the diffraction grating will be observed at an angle different fromthe angle of observing the uneven structure in the first region R1. Thisconfiguration can produce a display that provides a different imageaccording to observation angles. Instead of or in addition to thediffraction grating, a scattering structure may be provided in thesecond region R2. Providing the scattering structure reduces (decreases)the chroma of the uneven structure in the first region R1, that is, thechroma can be controlled according to an area ratio between thescattering structure and the uneven structure. In the example shown inFIG. 1C, the first region group G includes an uneven structure havingthe flat part 4 b and the concavities 4 a in the first region R1, andhas a flat structure in the second region R2.

Details of the uneven structure in the first region R1 of theuneven-structure-forming layer 4 will be described later in the section“Uneven structure in a first region R1 of the uneven-structure-forminglayer 4”.

Examples of the material that can be used as theuneven-structure-forming layer 4 include a thermoplastic resin or aphoto curable resin.

(Reflecting Layer 6)

The reflecting layer 6 serves as a layer that reflects light.

The reflecting layer 6 covers at least part of the surface on which theuneven structure of the uneven-structure-forming layer 4 is provided. Aswill be described later, a structural color is produced by reflection oflight from the uneven structure of the uneven-structure-forming layer 4;hence the reflecting layer 6 preferably covers a region that displaysthe structural color. From this point of view, it is preferred that thereflecting layer 6 covers a whole region where the uneven structure isformed when the region that displays the structural color agrees withthe region where the uneven structure is formed. When the region thatdisplays the structural color serves as part of the region where theuneven structure is formed, however, it is preferred that the reflectinglayer 6 covers part of the region. As in the example shown in FIG. 6,when the concavities 4 a are disposed in part of the first region R1,the reflecting layer 6 does not necessarily have to be provided in theflat part 4 b at the right end of the first region R1, which is assumednot to participate in displaying the structural color. Further, as inthe example shown in FIG. 11, when the first region group G includes aflat region F, the reflecting layer 6 does not necessarily have to beprovided in the flat region F. Thus, providing the reflecting layer 6 inpart of the surface on which the uneven structure of theuneven-structure-forming layer 4 controls unwanted reflected light andimproves the contrast of a displayed image.

The reflecting layer 6 may have a substantially even film thickness,while being formed conforming to the uneven structure of theuneven-structure-forming layer 4. In this case, the surface of thereflecting layer 6 on a side opposite to the surface that is in contactwith the uneven-structure-forming layer 4 will have a shape similar tothat of the uneven structure of the uneven-structure-forming layer 4.The surface of the reflecting layer 6 on the opposite side to thesurface that is in contact with the uneven-structure-forming layer 4,however, may be flat. In this case, the reflecting layer 6 will have anuneven film thickness.

Examples of the material that can be used as the reflecting layer 6include metals such as aluminum, silver, gold, and alloys thereof.Alternatively, the reflecting layer 6 may be a dielectric layer having arefractive index different from that of the uneven-structure-forminglayer 4. Alternatively, the reflecting layer 6 may be a laminatecomposed of dielectric layers each having a refractive index differentfrom that of an adjacent dielectric layer. In other words, thereflecting layer 6 may be a dielectric multilayer film. When adielectric multilayer film is used, the refractive index of thedielectric layer that is in contact with the uneven-structure-forminglayer 4 is preferably different from that of theuneven-structure-forming layer 4.

(Other Layers)

The display 10 of the present invention may further include other layerssuch as an adhesive layer, a resin layer and a printed layer.

The adhesive layer can be provided, for example, so as to cover thereflecting layer 6. Normally, the surface of the reflecting layer 6 hasa configuration that is almost identical to an uneven configuration ofthe interface between the uneven-structure-forming layer 4 and thereflecting layer 6. Providing an adhesive layer can prevent the surfaceof the reflecting layer 6 from being exposed. Therefore, it is difficultto duplicate the uneven configuration of the interface for the purposeof counterfeit.

The resin layer is, for example, a hard coat layer that prevents thesurface of the display 10 from being damaged when the display 10 is inuse, an antifouling layer that prevents attachment of dirt, ananti-reflecting layer that prevents light from reflecting off a surfaceof the substrate, and an antistatic layer. The resin layer can beprovided on a front surface of the display 10. For example, when theuneven-structure-forming layer 4 side is taken to be a rear side and thereflecting layer 6 side serves as a front side, covering the reflectinglayer 6 with the resin layer can not only control damage of thereflecting layer 6 but can also make it difficult to duplicate theuneven structure for counterfeiting as well.

The printed layer is provided to display an image such as of a letter, apicture, or a symbol. The printed layer may be provided on a surface ofthe substrate 2 opposite to the surface on which theuneven-structure-forming layer 4 is provided between theuneven-structure-forming layer 4 and the reflecting layer 6, or on arear surface of the reflecting layer 6. The printed layer may also beprovided being or not being overlapped with the first region R1 in planview. Different kinds of ink such as offset ink, letterpress ink andgravure ink are used depending on printing methods. These kinds of inkcan be classified into resin-based ink, oil-based ink, water-based ink,and the like according to compositions thereof, or can be classifiedinto oxidation polymerization type ink, penetration drying type ink,evaporation drying type ink, ultraviolet curing type ink, and the likeaccording to drying methods thereof. The kind of ink to be used isselected as appropriate depending on the type of the substrate 2 and theprinting method. Besides normal colored ink, special ink such as light(e.g., fluorescent light)-emitting ink, cholesteric liquid crystal ink,or pearl ink may be selected as a material of the printed layer. Theprinted layer formed of the pearl ink can produce a color relativelysimilar to the structural color expressed by the display 10. Therefore,applying the printed layer formed of the pearl ink can provide a partfor displaying iridescent change due to the structural color and theperiodic structure and a part for displaying only a color similar to thestructural color. This can further complicate the color production ofthe display, which can in turn make counterfeiting more difficult.

(Uneven Structure in a First Region R1 of the Uneven-Structure-FormingLayer 4)

Now a description will be given of an uneven structure in a first regionR1 of the uneven-structure-forming layer 4.

The uneven structure in the first region R1 serves as a basic unit of anuneven structure in the first region group G.

FIG. 2 is a view schematically illustrating an example of the unevenstructure in a first region R1 of the uneven-structure-forming layer 4,i.e. an enlarged view of the first region R1 shown in FIG. 1B.

In FIG. 2, the bottom surface of the concavity 4 a has a square shape inplan view. In the present invention, however, the shape of the bottomsurface of each concavity 4 a (or the top surface of each convexity) isnot limited to a square shape, but may be formed in any shape. Examplesof the shape that can be adopted as the shape of the bottom surface ofthe concavity 4 a include a triangle, a quadrant such as a rectangle anda trapezoid, a polygon such as a pentagon and a hexagon, a circle, anellipse, a star, a cross, and an L shape. Alternatively, concavities 4 aof a different shape may be mixedly provided in the first region R1.Further, the bottom surfaces of the concavities 4 a (or the top surfacesof the convexities) may be similar to each other in shape but with adifferent size. As in the example shown in FIG. 3, the bottom surface ofthe concavities 4 a (or the top surface of convexities) may partiallyoverlap with that of other concavities 4 a (or of other convexities).

As described above, the bottom surface of the concavities 4 a (or thetop surface of the convexities) may be formed into any shape. However,all the bottom surfaces preferably have an identical shape to intensifythe diffracted light in a specific direction for improved observation ofthe iridescent change due to the periodic structure. From the aspect ofease in manufacture, each of the concavities 4 a preferably has arectangular shape, and more preferably has a quadrangular shape.

In the example shown in FIG. 2, seven concavities 4 a are arranged suchthat the sides of the bottom surface of each square concavity 4 a areoriented in the X or Y direction. The arrangement is, however, notlimited to this in the present invention. For example, the concavities 4a (or convexities) may be arranged such that the sides of the bottomsurface of each concavity 4 a (or the top surface of each convexity) aredifferently oriented from other concavities 4 a (or convexities).

The long side and the short side of the top surface of each convexity orof the bottom surface of each concavity of the uneven structure may haverespective lengths, for example, of 0.3 μm-10 μm, and preferably 0.3μm-5 μm. The long and the short sides are defined herein as follows.First, the longest line segment connecting two points on an outline ofthe bottom surface of a concavity (or the top surface of a convexity) isdefined as the long side. Then, a rectangle circumscribing the outlineof the bottom surface of the concavity (or the top surface of theconvexity) having a side parallel to the long side is drawn, and thisshorter side is defined as the short side of the bottom surface of theconcavity (or the top surface of the convexity). When the bottom surfaceof the concavity (or the top surface of the convexity) is, for example,a square where all the lengths and internal angles of the sides areequal, the long side and the short side have an equal length.

In the uneven structure of the first region R1 in the display 10 of thepresent invention, the distances between the centers of adjacentconcavities 4 a (or convexities) are not equal. The distances betweenthe centers of adjacent concavities 4 a (or convexities) refer to alength connecting the centers or the gravity centers of the bottomsurfaces (or top surfaces of the convexities) of the adjacentconcavities 4 a.

The bottom surface of each concavity 4 a or the top surface of eachconvexity is substantially parallel to the surface of the flat part 4 b.Further, the bottom surface of each concavity 4 a or the top surface ofeach convexity, and the surface of the flat part are smooth.

The convexities or concavities in the first region R1 may be arranged inany way as long as adjacent convexities or concavities have centersregularly distanced from each other. As shown in FIG. 2, for example,the convexities or concavities can be randomly provided in the firstregion R1 (hereinafter also referred to as “random arrangement”). Theconvexities or concavities may also be arranged in a specific directionsuch that the distances between the centers of convexities orconcavities, which are adjacent in the specific direction become random(hereinafter also referred to as “anisotropic arrangement”). The“specific direction” here refers to a predetermined one selecteddirection in an XY plane. As shown in FIG. 4, for example, theconcavities 4 a may be arranged side by side in the X direction, whichis a specific direction. As shown in FIG. 5, the concavities 4 a mayalso be arranged in an oblique direction, which is also a specificdirection. Such an arrangement can control the scattering directions oflight. Therefore, this arrangement can change the visibility of theimage between when observed in the arrayed direction of the concavities4 a and when observed in the direction orthogonal thereto. Theconvexities or concavities do not need to be arranged all over the firstregion R1. For example, as shown in FIG. 6, the convexities orconcavities may be arranged in part of the first region R1. Although theconvexities or the concavities are thus arranged in a part of the firstregion R1, the color change due to the periodic structure is similar tothat in the case where the convexities or the concavities are arrangedall over the first region R1. This is because the first regions R1,which are provided with the convexities or the concavities, are arrangedat a regular pitch. However, the structural color will have a lowerbrightness because the occupancy of the top surface of the convexity orthe bottom surface of the concavity is reduced in the first region R1

In the present invention, the uneven-structure-forming layer 4 mayfurther have convexities or concavities each defining the first regionR1, on the uneven structured surface. In the example shown in FIG. 7, alinear concavity 4 c is provided around the first region R1 to definethe first region R. This intensifies the diffracted light, making iteasier to observe the iridescent change due to the periodic structure ofthe first region R1.

In the first region R1, the convexities or concavities have a uniformheight and depth relative to a surface of the flat part, for example,0.05 μm-0.5 μm, and preferably 0.07 μm-0.4 μm. The height of theconvexities or the depth of the concavities affects diffractionefficiency. When the height of the convexities falls within the aboverange, the display 10 appears bright. If the height (depth) of theconvexity (concavity) is too short, a specific wavelength region is lessinfluenced by light interference which depends on the depth (height)between the concavity 4 a (or convexity) and the flat part 4 b.Accordingly, it is difficult to display the structural color. Inaddition, an external factor in a manufacturing process, such as a statevariation in manufacturing equipment, a variation in surroundings, and aslight change in a material composition, has a large effect on opticalproperties of the uneven structure. However, if the depth (height) ofthe concavity 4 a (or convexity) is too long, a wavelength of theinterfering light depending on the depth (height) between the concavity4 a (or convexity) and the flat part 4 b varies too widely depending onobservation angles, resulting in too great color change depending on theobservation directions. Accordingly, the observer cannot easilyrecognize the structural color. Also, if the depth (height) of theconcavity 4 a (or convexity) is too long, difficulty is involved informing the uneven structure with high accuracy in shape and dimension.

The height of the convexities or the depth of the concavities that isuneven relative to the surface of the flat part in the first region R1causes interference of light of all wavelengths in the visible region.As a result, light having various wavelengths evenly reaches theobserver's eyes, which disables the observer from perceiving aparticular color corresponding to the depth of the concavity or theheight of the convexity, only to perceive it as a white color. Asdescribed later, the display of the present invention has a periodicarrangement of the first region R1 provided with the uneven structure,and thus produces a color change due to the periodic structure. In thiscolor change, the height of the convexities or the depth of theconcavities that is uneven relative to the surface of the flat part inthe first region R1 causes the diffraction efficiency to vary, making itharder to recognize the color change due to the periodic structure. Inother words, it becomes difficult to observe the iridescence due to theperiodic structure.

The side surface of the concavity 4 a (or the convexity) issubstantially perpendicular to the bottom surface of the concavity 4 a(or the top surface of the convexity).

The top surface of the convexity or the bottom surface of the concavityoccupies, for example, a 20%-80%, and preferably 40%-60%, area of thefirst region R1. An area where the structural color can be displayed ismaximized when an area of the top surface of the convexity or the bottomsurface of the concavity and an area of the flat part have a ratio of1:1, so that the brightest structural color is displayed when theconvexity or the concavity occupies an approximately 50% area of thefirst region R1. An area occupation ratio of 20%-80% achieves colorproduction that is sufficiently bright.

(Uneven Structure in the First Region Group G of theUneven-Structure-Forming Layer 4)

Now a description will be given on the uneven structure in the firstregion group G of the uneven-structure-forming layer 4.

An uneven structure in the first region group G of theuneven-structure-forming layer 4 is formed by arranging at a regularpitch the uneven structures in the first region R1 of theuneven-structure-forming layer 4 described above. The uneven structurein the first region R1 serving as a basic unit, the uneven structure inthe first region group G is therefore a repetitive arrangement of thebasic unit. In the present invention, however, the uneven structure ofthe first region group G may also be formed by use of concavities 4 a(or convexities) as the uneven structure of the first region R1, thenumber of concavities 4 a whose number being the only difference.

Initially described below is an embodiment in which repeatedly arrangingthe uneven structure in the first region R1, which serves as a basicunit, forms the uneven structure of the first region group G.

FIGS. 8 to 10 are views each schematically illustrating an example ofthe uneven structure in the first region group G. The first region groupG shown in FIG. 8 includes four first regions R1 in total; two firstregions R1 each having a square-outer shape are arranged respectively inthe X and Y directions in plan view. Each of the four first regions R1is provided with an identical uneven structure that includes sevenconcavities 4 a and a flat part 4 b surrounding the concavities 4 a. Theouter shape of the first region R1 in the example shown in FIG. 8 isformed into a rectangle in the example shown in FIG. 9. In the exampleshown in FIG. 10, the first regions R1 whose outer shape is anequilateral hexagon are closely arranged. The “outer shape” of the firstregion R1 refers to a shape formed by a virtual line provided to definethe first region R1. A dash-dot-dot line is used in the accompanyingdrawings to clarify the outer shape of the first region R1, but such aline is not actually present.

The outer shape of the first region R1 is not limited to those shown inFIGS. 8 to 10. Examples of other kinds of outer shape include atriangle, a tetragon such as a parallelogram and a trapezoid, apentagon, and other polygon. A square and a rectangle are preferable interms of ease of manufacture.

An uneven structure in the first region group G of theuneven-structure-forming layer 4 is formed by arranging at a regularpitch the uneven structures in the first region R1 of theuneven-structure-forming layer 4. The arrangement at a regular pitchmeans here that the first regions R1 are periodically arranged in atleast one direction. For example, in the example shown in FIG. 8, thefirst regions R1 each have a square-outer shape having a side length P,and are closely arranged without cavities therebetween. The firstregions R1 are therefore arranged at a pitch P in the X and Ydirections. In the example shown in FIG. 9, the first regions R1 eachhave a rectangular outer shape having a short side length P₁ and a longside length P₂, and are closely arranged without cavities therebetween.The first regions R1 are therefore arranged at a pitch P₁ in the Xdirection and at a pitch P₂ in the Y direction.

In the present invention, the first regions R1 are arranged at a regularpitch. The arrangement at a regular pitch causes the display 10 toproduce a color change (diffracted light) caused by the periodicstructure. Note that the arrangement pitch of the first region R1 ispreferably 1 μm-300 μm on an occasion when the observer uses afluorescent light, sunlight, and other parallel light, an LED(light-emitting diode) light and other point light source, laser lightand others to visually recognize the diffracted light. Arranging thefirst regions R1 at a pitch within this range, the person observing thedisplay 10 can recognize the color change (diffracted light) caused bythe periodic structure, the color change occurring as an observationangle varies, and the structural color caused by the scattered light. Atoo narrow arrangement pitch of the first region R1 increases the colorchange due to the periodic structure, possibly posing a risk that theobserver fails to correctly recognize the structural color caused by thescattered light. Hence the arrangement pitch of the first region R1 ispreferably 5 μm-300 μm, and more preferably 8 μm-300 μm.

When diffracted light falling within or out of the visible light rangeis detected by, for example, a machine, the arrangement pitch of thefirst region R1 is not limited to the range of 1 μm-300 μm. For example,on an occasion when the arrangement pitch of the first region R1 isbelow 1 μm, the diffracted light within the ultraviolet range can bemachine-detected by use of a light source having a wavelength shorterthan that of ultraviolet light. Using a light-receiving member made offluorescent material makes it possible to visually check the diffractedlight within the ultraviolet range based on a fluorescent state of thelight-receiving member. When the arrangement pitch of the first regionR1 is above 300 μm, image analysis or other approach can visuallyconfirm the presence of the diffracted light in the visible light range,which is hard to visually determine. Further, the presence of thediffracted light in a range having a wavelength longer than that ofultraviolet light is confirmed by use of a corresponding photodetectingelement.

In visual observation of the color change caused by the periodicstructure, the extent of the color change that can be recognized mayvary depending on light source to be used. The arrangement pitch of thefirst region R1 may be thus set to an appropriate length depending onwhich light source to be used. The light sources for observing thedisplay 10 incidentally include sunlight, a fluorescent light and otherparallel light, an LED light and other point light source, and a laserlight source.

For example, at a time of observation under parallel light such assunlight or fluorescent light, the arrangement pitch of the firstregions R1 is preferably set to 1 μm-30 μm. In observation under an LEDlight or other point light source, the arrangement pitch of the firstregions R1 is preferably 1 μm-100 μm, and more preferably 1 μm-80 μm. Inobservation under a laser light source, the arrangement pitch of thefirst regions R1 is preferably 1 μm-300 μm. Note that the range of 1μm-30 μm, which all the above preferred ranges cover in common, makes itpossible to confirm the color change caused by the periodic structure,regardless of which light source is used.

The observation under the point light source and the laser light can beincidentally said to be observation in an environment applied by aninspector, who is a trained expert. The observation under laser lightis, in particular, observation in a special environment because thelaser light requires a laser light emitter and other special equipmentunlike point light sources, which are now relatively accessible due towidespread use of LED lights. Setting the arrangement pitch of the firstregions R1 as appropriate so that the color change caused by theperiodic structure cannot be observed under parallel light but can beobserved under a point light source or the laser light or so that thecolor change caused by the periodic structure cannot be observed underparallel light and a point light source but can be observed under laserlight makes it hard for an ordinary person to determine theauthenticity, which in turn further improves the anti-counterfeitingeffects. A preferable arrangement pitch of the first regions R1 formaking it hard to observe the color change under parallel light and easyto observe the color change under a point light source is 30 μm-100 μm,and more preferably to 30 μm-80 μm. A preferable arrangement pitch ofthe first regions R1 for making it hard to observe the color changeunder parallel light and easy to observe the color change under laserlight is 30 μm-300 μm. A preferable arrangement pitch of the firstregions R1 for making it hard to observe the color change under parallellight and the point light source and easy to observe the color changeunder laser light is 80 μm-300 μm, and more preferably to 100 μm-300 μm.

Further, the first regions R1 may be arranged with a gap therebetween inthe present invention. Examples of this arrangement are shown in FIGS.11 and 12.

In the example shown in FIG. 11, the first regions R1 are arrangedalternately with the flat region F. In the figure, the first region R1and the flat region F both have square-outer shapes each having a sidelength P. The first regions R1 are therefore arranged at a pitch 2P inthe X and Y directions.

In the example shown in FIG. 12, the first regions R1 and the flatregions F are arranged adjacent to each other in the Y direction, andthe first regions R1 and the flat regions F are alternately arranged inthe X direction. In the figure, the first region R1 and the flat regionF both have square-outer shapes each having a side length P. The firstregions R1 are therefore arranged at the pitch 2P in the X direction andat the pitch P in the Y direction.

When the flat regions F are thus combined with the first regions R1, thefirst regions R1 occupy less of the first region group G than on anoccasion when no flat region F is combined. Since the brightness of thestructural color depends on an area ratio of the concavities or theconvexities provided in the first region R1, a lower ratio of the firstregion R1 lowers the brightness of the structural color. This means alonger arrangement pitch of the first regions R1, which makes it harderto recognize the iridescence change due to the periodic structure. Thuscombining the flat regions F with the first regions R1 can produce acolor different from the color produced on the occasion when no flatregion F is combined.

In the present invention, the uneven structure of theuneven-structure-forming layer 4 may be formed by combination ofdifferent first region groups. In the different first region group, theuneven structure in the first region R1, which serves as the basic unit,is different or the arrangement pitch of the first regions R1 isdifferent. “The uneven structures are different” means here that atleast one of the followings is different: a shape of the bottom surfaceof the concavities 4 a (or the top surface of the convexities) describedin the above section “Uneven structure in a first region R1 of theuneven-structure-forming layer 4”, the arrangement of the concavities(or the convexities), the height of a long side and a short side of thebottom surface of the concavities, the depth of the concavities (or theheight of the convexities), and a ratio which the top surface of theconvexities or the bottom surface of the concavities occupies in thefirst region R1.

Examples of a combination of the different first region groups are shownin FIGS. 13 and 14.

The example shown in FIG. 13 is formed by a combination of two kinds offirst region groups, i.e., a first region group G1 including a firstregion R1-1 and a first region group G2 including a first region R1-2.In the first region group G1 including the first regions R1-1, the firstregions R1-1 are arranged at a pitch P in the Y direction and arearranged at a pitch 2P in the X direction. In the first region group G2constituted by the first regions R1-2 as well, the first regions R1-2are arranged at a pitch P in the Y direction and are arranged at a pitch2P in the X direction. Note that the first region R1-1 and the firstregion R1-2 respectively correspond to the first region R1 shown inFIGS. 4 and 5.

In the example shown in FIG. 13, observing a display surface of thedisplay 10 either in the X direction or in the Y direction makessubstantially no difference in how the structural color appears becausethe concavities have a uniform depth. In contrast, the arrangementpitches of the first regions R1-1 and R1-2 are different between the Xdirection and the Y direction. More specifically, the first regions R1-1and R1-2 are arranged at the pitch 2P in the X direction and at thepitch P in the Y direction. This means that a diffraction angle ofdiffracted light emitted in the X direction is approximately a half of adiffraction angle of diffracted light emitted in the Y direction, whichmakes a difference in how the color change caused by the periodicstructure appears between the observation in the X direction and theobservation in the Y direction. For example, in FIG. 13, assuming thatthe first regions R1-1 and R1-2 are arranged at 160 μm in the Xdirection and 80 μm in the Y direction. In this case, if a point lightsource is used to irradiate the display, the color change caused by theperiodic structure cannot be observed in the Y direction, though it canbe observed in the X direction. Arranging the first regions such thatthe pitch lengths differ depending on directions can make a differencein how the color change caused by the periodic structure looks.

The example shown in FIG. 14 is formed by a combination of three kindsof first region groups, more specifically, by a combination of a firstregion group G1 in which the first regions R1-1 are arranged in thepitch P in the X and Y directions, a first region group G2 in which thefirst regions R1-1 are arranged in a pitch 2P in the X and Y directions,and a first region group G3 in which the first regions R1-2 are arrangedat the pitch 2P in the X and Y directions. Note that the first regionR1-1 and the first region R1-2 respectively correspond to the firstregion R1 shown in FIGS. 4 and 5.

As described above, the first region group G1 has a pitch of the firstregion R1-1 in the X and Y directions, a pitch with a half-length ofthat in the first region group G2 and the first region group G3, whichmakes it is easier to observe the iridescent change.

The iridescent change is more prominent when an LED light and otherpoint light source is used compared to the case where a fluorescentlight and other parallel light is used.

In the example of FIG. 14, combining the first region groups G1, G2, andG3, each having a different arrangement pitch of the first region R1-1,to form a symbol also makes it possible to observe a symbol under theLED light, a symbol that cannot be observed under the fluorescencelight, though it depends on how long the arrangement pitch is. Hence, byusing a fluorescent light and an LED light as appropriate, an imagewhose symbol varies iridescently can be formed. This is a simple methodto confirm the presence of the symbol because fluorescent lights and LEDlights are light sources used by the general public.

In the example shown in FIG. 14, using the first regions R1-1 eachhaving an identical outer shape and size (a square with a side length P)in the first region group G1 and the first region groups G2 and G3 andchanging how the first regions R1-1 are arranged to differentiate thepitches, but this is not the only approach. The pitch of the firstregion R1-1 may be differentiated by use of the first regions R1-1 eachhaving a different outer shape and/or size in each first region group.

Forming the uneven structure of the uneven-structure-forming layer 4from a combination of a plurality of mutually different first regiongroups makes it possible to manufacture a display applied to a varietyof designs.

Next, an embodiment where the uneven structure of the first region groupG is formed by use of an uneven structure, as the uneven structures ofthe first region R1, where the number of concavities 4 a (orconvexities) is the only difference.

In the example shown in FIG. 15, the number of the concavities 4 a ineach first region R1 gradually decreases from the upper left end to thelower right end of the first region group G. In addition, the number ofthe concavities 4 a in each first region R1 remains unchanged orgradually decreases in the X and Y directions. As described above, thefirst region group G has uneven structures in which the number of theconvexities or concavities in the first region R1 remain unchanged orgradually decreases or increases in the specific direction in thepresent invention. The “specific direction” here refers to apredetermined one or a plurality of arbitrary direction(s) in the XYplane. The present invention does not only include the mode in which thenumber of the concavities 4 a (or convexities) in each first region R1gradually changes in the specific direction but also a mode in whichfirst regions R1 each having an equal or different number of concavities4 a (or convexities) are randomly combined.

The number of the concavities (or convexities) is the only differencebetween the first regions in the present embodiment. As in the casewhere an identical number of concavities (or convexities) are arrangedin each first region, therefore, the iridescent change due to theperiodic structure and the representation of the structural color can beachieved. In particular, when the number of concavities is graduallyvaried in each first region R1 in a specific direction as in the exampleshown in FIG. 15, the intensity of the diffracted light and thebrightness of the structural color caused by the periodic structure canbe gradually varied.

Providing the first area group G described above in accordance with ashape of, for example, a desired letter, a figure, and a symbol candisplay the letters and others on the display 10 in color.

In the example shown in FIG. 1A, the display 10 displays characters 8 of“T”, “O”, and “P”. Each of the letters 8 is constituted by a firstregion group G where the plurality of first regions R1 is regularlyarranged. Note that, as shown in the figure, a first region R1 that hasan outline of the letter 8 can assume an outer shape along the outline.In FIG. 1B, a region other than a letter part is a second region R2,which has a flat structure.

In the present invention, the uneven-structure-forming layer 4 may beformed by provision of different first region groups G for each sectionwhere letters and designs are displayed. For example, theuneven-structure-forming layer 4 may be formed by provision of firstregion groups G each having concavities (or convexities) whose depth (orheights) are different for each section where letters and designs aredisplayed. The uneven-structure-forming layer 4 may also be formed byprovision, for each letter or design section, of a first region group Ghaving a plurality of the first regions R1 where the convexities orconcavities are randomly arranged and a first region group G having aplurality of the first regions R1 where the convexities or concavitiesare anisotropically arranged. In addition, the uneven-structure-forminglayer 4 may be formed by provision, for each letter or design section,of a first region group G having first regions R where the convexitiesor concavities are anisotropically arranged. For example, in the exampleshown in FIG. 1, “T” can be formed as a basic unit of the randomlyarranged uneven structure of FIG. 2, “O” can be formed as a basic unitof the anisotropically arranged uneven structure of FIG. 4, and “P” canbe formed as a basic unit of the anisotropically arranged unevenstructure of the FIG. 5.

Note that the various embodiments and modifications described above canbe applied in combination of two or more of them.

(Visual Effect of the Display 10)

In the display 10 of the present invention, the uneven-structure-forminglayer 4 has a first region group G constituted by a plurality of firstregions and has a specific uneven structure in the first region R1. Inaddition, the first regions R1 are arranged at a regular pitch. As aresult, the display 10 of the present invention exhibits the iridescentchange due to the periodic structure in accordance with a variation inthe observation angle, and represents a color with high chroma(structural color) caused by light interference according to the depthsof concavities 4 a and flat parts 4 b (or the heights of theconvexities). Its principles will be described below.

First, here is the reason why the display 10 of the present inventionexhibits a color change according to the variation in the observationangle.

Irradiating the diffraction grating by use of an illumination lightsource causes the diffraction grating to emit strong diffracted light ina specific direction according to a traveling direction and wavelengthof the illumination light, which serves as incident light.

In a circumstance where the light travels in a plane perpendicular to alongitudinal direction of a groove of the diffraction grating, anemission angle β of an m-th order diffracted light (m=0, ±1, ±2, . . . )can be calculated by the formula below.d=mλ/(sin α−sin β)   (Equation 1)

In the Equation 1, “d” represents a grating constant (grating pitch) ofthe diffraction grating, “m” represents a diffraction order, and “λ”represents wavelengths of the incident light and the diffracted light.In addition, “α” represents an emission angle of zero-order diffractedlight, that is, specularly reflected light RL. In other words, anabsolute value of α is equal to an incident angle of the illuminationlight. As for a reflective diffraction grating, an incident direction ofthe illumination light and an emission direction of the specularlyreflected light are symmetrical about a normal NL of an interface wherethe diffraction grating is provided.

Note that, when the diffraction grating is of a reflection type, theangle α is 0° or greater and below 90°. Assuming that two angle rangeswhere illumination light is emitted in an oblique direction relative tothe interface where the diffraction grating is provided and the angle inthe normal direction, or 0°, is taken as a boundary value. In this case,the angle β is a positive value when the emission direction of thediffracted light and the emission direction of the specular reflectionlight fall within an identical angle range while it is a negative valuewhen the emission direction of the diffracted light and the incidentdirection of the illumination light fall within an identical anglerange.

FIG. 16 is a view schematically illustrating how the diffraction gratingemits primary diffracted light.

A point light source LS emits white light including a light component Rwhose wavelength falls within a red range, a light component G whosewavelength falls within a green range, and a light component B whosewavelength falls within a blue range. The light components G, B, and Remitted by the point light source LS are incident on a diffractiongrating GR at an incident angle α. The diffraction grating GR emits adiffracted light DL_g at an emission angle β_g as a part of the lightcomponent G, emits a diffracted light DL_b at an emission angle β_b as apart of the light component B, and emits a diffracted light DL_r at anemission angle β_r as a part of the light component R. Although notillustrated, the diffraction grating GR emits diffracted light ofanother order at an angle derived by the Equation 1.

Thus under predetermined illumination conditions, the diffractiongrating emits diffracted light at different emission angles according tothe wavelength thereof. Hence under a white light source such assunlight and fluorescent light, the diffraction grating emits light ofdifferent wavelengths at different angles. Under such illuminationconditions, therefore, the display color of the diffraction gratingvaries iridescently.

In the display 10 of the present invention, an uneven structure isprovided on the surface of the uneven-structure-forming layer 4. Thisuneven structure is provided in a first region R1 on the surface of theuneven-structure-forming layer 4. The first regions are regularlyarranged at regular pitches. From the above description, it can be saidthat, in the display 10 of the present invention, theuneven-structure-forming layer 4 has concavities 4 a (or convexities)arranged at regular pitches. Further describing this with reference tothe example shown in FIG. 8, the first regions R1 provided with sevenconcavities 4 a are arranged in the X and Y directions at the pitch P.Focusing on each of the seven concavities 4 a, it can be said that eachof the concavities 4 a is regularly arranged at the pitch P in the X andY directions between the first regions R1.

Hence, as with a normal diffraction grating, changing an angle at whichof the display surface is observed causes diffracted light havingdifferent wavelengths to sequentially reach an observer's eyes in thedisplay 10 of the present invention as well, which causes the observerto recognize that the display surface varies iridescently.

Next, here is the reason why the display 10 of the present inventiondisplays a color with high chroma by virtue of scattered light.

FIG. 17 is a view schematically illustrating how the uneven structure ina first region R1 of the uneven-structure-forming layer 4 emitsscattered light. In the example shown in FIG. 17, the uneven structurehas the flat parts 4 b and the concavities 4 a. The concavities 4 a arearranged such that the distances between the centers thereof are not tobe equal. Incidence of illumination light on such irregularly arrangeduneven structures causes emission of diffracted light in variousdirections, as well as emission of regularly reflected light. Hence somevariation in the observation direction does not result in major colorchange of the display color. The observer then perceives a coloraccording to the depth of the concavities or the height of theconvexities. Described below is how the color perception occurs.

FIG. 18 is a view schematically illustrating how illumination light,which is incident on an uneven structure provided in a first region R1and reflects at a flat part 4 b and a bottom surface of a convexity 4 a.As shown in FIG. 18, when illumination light IL, which is incident onthe uneven structure at an angle θ, an optical path difference between alight RL₁ reflected by the bottom surface of the concavity 4 a and thelight RL₂ reflected by the flat part 4 b is twice a product of a depthdp of the concavity 4 a relative to the surface of theuneven-structure-forming layer 4, cos θ, and a refractive index n of theuneven-structure-forming layer 4. Hence, a phase difference between thelight RL₁ and the light RL₂ is 4πndp cos θ/λ, which is the optical pathdifference 2ndp cos θ multiplied by 2π/λ.

When the phase difference is an integer multiple of 2π, the lights RL₁and RL₂ create constructive interference. In this case, the unevenstructure therefore emits specularly reflected light RL with highintensity and diffracted light DL with low intensity.

When the phase difference is equal to a sum of 2π multiplied by aninteger and π, the lights RL₁ and RL₂ create destructive interference.In this case, the uneven structure therefore emits specularly reflectedlight RL with low intensity and diffracted light DL with high intensity.

At some extent of the depth of the concavities or the height of theconvexities, light of a certain wavelength within the visible rangecreates constructive interference while light of another wavelengthwithin the visible range creates destructive interference.

When the concavities have a uniform depth or the convexities have auniform height as in the present invention, diffraction is lessefficient in some wavelength region within the visible wavelength rangethan in the other wavelength regions.

Hence, when the uneven structure of a first region R1 is illuminatedwith illumination light, the observer perceives a particular coloraccording to the depth of the concavities or the height of theconvexities.

For example, assuming that diffraction efficiency of blue (a 460-nmwavelength) light is low, and red (a 630-nm wavelength) and green (a540-nm wavelength) wavelength components of the diffracted light reachesthe eyes of the observer at a time of observation of the first region R1provided with concavities of a certain depth, yellow is observed. Forexample, assuming that diffraction efficiency of red light is low, andgreen and blue wavelength components of the diffracted light reaches theeyes of the observer at a time of observation of the first region R1provided with convexities of another depth, cyan is observed.

In the example shown in FIG. 1, leveling out all the depths of theconcavities 4 a arranged in the character portions of “T”, “O”, and “P”makes it possible to display all the letters 8 in an identicalstructural color. Alternatively, arranging the concavities 4 a havingdifferent depths for each letter 8 of “T”, “O”, and “P”, makes itpossible to display each letter in a different structural color. Inaddition, as shown in the current figure, dividing the letter “P” into“I” and “⊃” and arranging the concavities 4 a each having a differentdepth for each character makes it possible to display one letter indifferent structural colors.

As described above, changing the observation angle causes the display 10of the present invention to produce a color change caused by theperiodic structure, while displaying a structural color whose colorhardly changes, although the observation direction changes to somedegree. As described above, the display 10 of the present inventionprovides both a color change depending on the observation angle, and acolor change not much depending on the observation angle. Hence, thedisplay 10 provides very special visual effects. As a result, thedisplay 10 of the present invention exhibits improvedanti-counterfeiting effects compared with a conventional display thatonly displays structural color.

(Method of Manufacturing the Display 10)

Next, an exemplary method of manufacturing the display 10 of the presentinvention will be described.

First, an uneven-structure-forming layer 4 having an uneven structure onone surface is formed. Forming the uneven-structure-forming layer 4involves preparing a metallic stamper by use of photolithography asfollows.

The first step is to apply a photosensitive resist material to a smoothsubstrate (a glass substrate is generally used) to form an evenly thickresist material layer. Examples of the material that can be used as thephotosensitive resist material include a known positive or a negativetype material. The next step is to draw a desired pattern on the resistmaterial layer with a charged particle beam before developing thisresist material layer to produce an uneven structure.

The following step is to use this structure as an original plate toprepare a metallic stamper by electroforming or other method.Electroforming is a kind of surface treatment technique for forming ametal film on this object by immersing in a predetermined aqueoussolution the object to be electroformed and energizing the object byvirtue of the reducing power of electrons. Such a method makes itpossible to precisely duplicate a fine uneven structure provided on asurface of the original plate. Note that a surface of the object to beelectroformed needs to be electrically conductive. A metal thin filmshould be provided in advance on a surface of the structure by a vaporphase deposition method such as sputtering or vacuum deposition beforecarrying out the electroforming because photosensitive resists aregenerally non-conductive.

Then, by using this stamper, the uneven structure is duplicated. Morespecifically, duplicating the uneven structure follows, for example, thefollowing steps: first applying a thermoplastic resin or a photo curingresin on a transparent substrate 2 made of polycarbonate or polyester;then closely contacting the metal stamper with the coating film beforeheating or irradiating the resin layer in this state; and removing themetal stamper from the cured resin to produce anuneven-structure-forming layer 4, which has an uneven structure.

Photolithography is used as a method of manufacturing the original platein the above description, but using a fine-tipped diamond bite or othercutting tool and etching to corrode a surface of metal and othermaterial are also available as an alternative method. Such a method candirectly process a surface of the metal plate, which makes it possibleto directly prepare the metal stamper without having to form the metalstamper by electroforming and other method.

What to do next is to deposit aluminum and other metal or a dielectricinto a single layer or multilayer by, for example, vapor deposition toform a reflecting layer 6 on the uneven-structure-forming layer 4.Preparing a reflecting layer 6 that only covers a part of theuneven-structure-forming layer 4, or a patterned reflecting layer 6involves forming a reflecting layer 6 serving as a continuous film by,for example, the vapor phase deposition method before dissolving a partthereof with chemicals and the like. An alternative method of preparingthe patterned reflecting layer 6 is to form a reflecting layer 6 servingas a continuous film before removing a part of the reflecting layer 6from the uneven-structure-forming layer 4 by use of adhesive materialthat is more adhesive onto the reflecting layer 6 than onto theuneven-structure-forming layer 4. Further alternatively, the patternedreflecting layer 6 can be prepared through vapor phase deposition by useof a mask, or through a lift-off process.

The display 10 can be thus manufactured.

<Article with a Display>

The display 10 of the present invention described above can be used asan anti-counterfeiting label by being carried by printed objects andother articles. As described above, the display 10 provides specialvisual effects. In addition, it is hard to counterfeit the display 10.It is therefore hard to counterfeit or imitate an article with a displayin which the display 10 is carried by the article itself.

FIG. 19 is a schematic plan view illustrating an example of the articlewith a display of the present invention.

Examples of an article 12 to which the display 10 is attached include acard such as a magnetic card, an integrated circuit (IC) card, awireless card, and an identification (ID) card, passports, and avaluable stock certificate such as a gift ticket and a stockcertificate, and a paper currency. Alternatively, the article 12 may bea tag and a label to be attached to an article that should be confirmedas a genuine product. Other examples thereof may include a package or apart thereof that accommodates an article to be confirmed as a genuineproduct.

Examples of the substrate that can be used as a valuable stockcertificate or paper currency include a paper substrate, a substratemade of a resin or the like.

The article 20 with a display may be an article with the display 10being fixed to the substrate of the article 12 with an adhesive layer ora sticking layer therebetween. More specifically, the article 20 with adisplay may be an article with the display 10 being prepared in advanceas an adhesive sticker (label), a transfer foil, or a hologram sheet,the display 10 being fixed to the substrate. The adhesive sticker(label) has a configuration in which an adhesive layer or a stickinglayer is provided so as to be in contact with the reflecting layer 6 (apart from which the reflecting layer 6 is removed is theuneven-structure-forming layer 4). The transfer foil has a configurationin which a removable layer is provided between the substrate thatconstitutes the display 10 and the uneven-structure-forming layer and anadhesive layer or a sticking layer is provided so as to be in contactwith the reflecting layer 6 (a part from which the reflecting layer 6 isremoved is the uneven-structure-forming layer 4). Removing the substrateafter pasting the transfer foil to the article 12 can transfer thedisplay 10 to a surface of the article 12. The transfer foil may bestripe- or patch-shaped, and be applied to all over or a part of thearticle 12.

The display 10 can also be provided with a printed layer. The printedlayer can produce a color that is relatively similar to the structuralcolor developed by the display 10, while not providing an iridescentchange. Hence, in the display 10 provided with the printed layer, noiridescent change occurs in an area where the printed layer is provided,but iridescent change does occur in a first area group provided with theuneven structure of the uneven-structure-forming layer 4. Takingadvantage of this characteristic makes it possible to design a display10 having an area not producing iridescent change and an area producingiridescent change, though these areas may be recognized to be printedimages at first glance. Such a display 10 exhibits improvedanti-counterfeiting effects. In addition, using several light sources asappropriate can determine whether or not a target article is authenticat a time of observation of the display 10. For example, in an displayin which the first regions of the uneven-structure-forming layer 4 arearranged at a pitch of 30 μm-100 μm, the color of an image recognized asa printed image iridescently changes by use of an LED light whenobserved under a fluorescent light, which makes it possible to determineits authenticity. In addition, in a display in which the first regionsare arranged at a pitch of 100 μm-300 μm, the color of an imagerecognized as a printed image iridescently changes by use of a laserlight when observed under a fluorescent light, which makes it possibleto determine its authenticity.

Further, in the display 10 provided with the printed layer, matching ahue of the displayed color caused by the printed layer with a hue of thestructural color caused by the uneven structure of theuneven-structure-forming layer 4 further enhances theanti-counterfeiting effects.

Note that the printed layer may be provided as an adhesive sticker(label) or transfer foil after the display is attached or transferred tothe article. When the display is transferred as a transfer foil, theprinted layer can be formed on the removable layer.

When the article 12 has, for example, a printed layer on its substrate,the display 10 may be fixed on the printed layer of the substrate.Comparing optical effects of the display 10 with that of the printedlayer enables the article with the display 20 to stand out the opticaleffects of the display 10.

When the display 10 is fixed to the substrate, such as when paper isused as the substrate, the display 10 may be watermarked in the paperand the paper may open at a location corresponding to the display 10.The display 10 may also be embedded in the article 12. In this case, thedisplay 10 can be used as a thread.

The display 10 may be used for a purpose other than anti-counterfeiting.The display 10 can be used, for example, as a toy, learning material, anornament or the like.

REFERENCE SIGNS LIST

2 . . . Substrate; 4 . . . Uneven-structure-forming layer; 4 a . . .Concavity; 4 b . . . Flat part; 6 . . . Reflecting layer; 10 . . .Display; 12 . . . Article; 20 . . . Article with display; R1 . . . Firstregion; R2 . . . Second region; G, G1, G2, G3 . . . First region group

What is claimed is:
 1. A display comprising: an uneven-structure-forminglayer having an uneven structure on one surface; and a reflecting layerthat covers at least part of an unevenly structured surface of theuneven-structure-forming layer, wherein the uneven-structure-forminglayer includes a first region group including a plurality of firstregions, each first region including a flat part and a plurality ofconvexities or a plurality of concavities, a top surface of each of theconvexities or a bottom surface of each of the concavities issubstantially parallel to a surface of the flat part; for each of thefirst regions, the convexities of the plurality of convexities or theconcavities of the plurality of the concavities are irregularly arrangedon the flat part so that distances between the centers of adjacentconvexities or concavities are not equal in at least one directionparallel to the flat part; wherein the convexities have a uniformheight, or the concavities have a uniform depth; wherein the firstregions within the first region group are periodically arranged in atleast one direction parallel to the flat part_with a pitch of 1 μm-300μm; wherein each of the first regions is provided with an identicaluneven structure that includes the plurality of convexities or theplurality of concavities and the flat part surrounding the plurality ofconvexities or the plurality of concavities, and wherein the firstregion group further comprises a plurality of identical second regions,each of the second regions of the plurality of identical second regionshas the same outer shape as each of the first regions of the pluralityof the first regions, each second region includes a flat part and aplurality of convexities or a plurality of concavities, a top surface ofeach of the convexities or a bottom surface of each of the concavitiesbeing substantially parallel to a surface of the flat part, in each ofthe second regions, the convexities of the plurality of convexities orthe concavities of the plurality of the concavities are irregularlyarranged on the flat part so that the distances between the centers ofadjacent convexities or concavities are not equal in at least onedirection parallel to the flat part of the second region, the irregulararrangement of the convexities or the concavities is in the secondregions is different from the irregular arrangement of the convexitiesor the concavities in the first regions, the flat parts of the secondregions are parallel to the flat parts of the first regions; the firstregions and the second regions are periodically arranged in analternating manner in at least one direction parallel to the flat parts.2. An article with a display comprising the display of claim
 1. 3. Thedisplay of claim 1, wherein distances between the centers of adjacentconvexities or concavities are not equal in each of a first directionand a second direction, which is not parallel to the first direction,each of the first direction and the second direction is parallel to theflat part.
 4. The display of claim 1, wherein distances between thecenters of adjacent convexities or concavities are not equal in a firstdirection and distances between the centers of adjacent convexities orconcavities are equal in a second direction, which is not parallel tothe first direction, each of the first direction and the seconddirection is parallel to the flat part.
 5. The display of claim 1,wherein each of the first regions within the first region group has asquare outer shape, wherein the first regions within the first regiongroup are periodically arranged in each of a first direction and asecond direction, which is perpendicular to the first direction, with apitch in each of the first direction and the second direction being from1 μm to 300 μm; each of the first direction and the second direction isparallel to the flat part.
 6. The display of claim 5, wherein the pitchin the first direction is the same as the pitch in the second direction.7. The display of claim 1, wherein each of the first regions within thefirst region group has a rectangular outer shape, wherein the firstregions within the first region group are periodically arranged in eachof a first direction and a second direction, which is perpendicular tothe first direction, with a first pitch in the first direction and asecond pitch, which is not equal to the first pitch in the seconddirection, each of the first pitch and the second pitch being from 1 μmto 300 μm; each of the first direction and the second direction isparallel to the flat part; the first pitch and the second pitchcorrespond to dimensions of the rectangular outer shape in the firstdirection and the second direction respectively.
 8. The display of claim1, wherein an outer shape of each of the first regions within the firstregion group is an equilateral hexagon, so that the first regions withinthe first region group form a hexagonal honeycomb structure.
 9. Thedisplay of claim 1, wherein the first region group further comprises aplurality of identical flat regions, each of the flat regions of theplurality of identical flat regions has the same outer shape as each ofthe first regions of the plurality of the first regions, each of theflat regions of the plurality of identical flat regions is parallel tothe flat part of each of the first regions of the plurality of the firstregions, the first regions and the flat regions are periodicallyarranged in an alternating manner in at least one direction parallel tothe flat part.
 10. The display of claim 9, wherein the first regions andthe flat regions are periodically arranged in an alternating manner in afirst direction parallel to the flat part, the first regions arearranged adjacent to each other in a second direction, which is parallelto the flat part but is perpendicular to the first direction; the flatregions are arranged adjacent to each other in the second direction. 11.The display of claim 9, wherein the first regions and the flat regionsare periodically arranged in an alternating manner in each of a firstdirection and a second direction, which is perpendicular to the firstdirection, each of the first direction and the second direction isparallel to the flat part.
 12. The display of claim 1, wherein the firstregions and the second regions are periodically arranged in analternating manner in a first direction parallel to the flat parts, thefirst regions are arranged adjacent to each other in a second direction,which is parallel to the flat parts but is perpendicular to the firstdirection; the second regions are arranged adjacent to each other in thesecond direction.
 13. The display of claim 1, wherein the first regionsand the second regions are periodically arranged in an alternatingmanner in each of a first direction and a second direction, which isperpendicular to the first direction, each of the first direction andthe second direction is parallel to the flat parts.
 14. A displaycomprising: an uneven-structure-forming layer having an uneven structureon one surface; and a reflecting layer that covers at least part of anunevenly structured surface of the uneven-structure-forming layer,wherein the uneven-structure-forming layer includes a first region groupincluding a plurality of first regions, each first region including aflat part and a plurality of convexities or a plurality of concavities,a top surface of each of the convexities or a bottom surface of each ofthe concavities is substantially parallel to a surface of the flat part;for each of the first regions, the convexities of the plurality ofconvexities or the concavities of the plurality of the concavities areirregularly arranged on the flat part so that distances between thecenters of adjacent convexities or concavities are not equal in at leastone direction parallel to the flat part; wherein the convexities have auniform height, or the concavities have a uniform depth; wherein thefirst regions within the first region group are periodically arranged inat least one direction parallel to the flat part with a pitch of 1μm-300 μm; wherein each of the first regions is provided with anidentical uneven structure that includes the plurality of convexities orthe plurality of concavities and the flat part surrounding the pluralityof convexities or the plurality of concavities, wherein each of thefirst regions within the first region group has a square outer shape,wherein the first regions within the first region group are periodicallyarranged in each of a first direction and a second direction, which isperpendicular to the first direction, with a pitch in each of the firstdirection and the second direction being from 1 μm to 300 μm; each ofthe first direction and the second direction is parallel to the flatpart; and wherein the pitch in the first direction is the same as thepitch in the second direction.